The present invention is directed to electromagnetic antennas, and especially to electromagnetic antenna arrays employing a plurality of antenna elements known as patch antenna elements. Such patch antenna construction is advantageous in constructing antenna arrays that are known as steerable beam antennas. Steerable beam antennas employ fixed antenna elements, such as patch antenna elements, to xe2x80x9csteerxe2x80x9d loci of sensitivity (i.e., transmitting beams or bearings of reception) by establishing predetermined interference patterns among the various patch antenna elements. The desired predetermined interference patterns are commonly effected by imposing phase differences among the various patch antenna elements.
In today""s marketplace it is desirable that a small compact steerable beam and antenna device be available for communication, locating (e.g., radar) and other applications.
It is desirable that patch antenna elements in steerable beam antennas be closely or densely situated in order that maximum interaction among the various patch antenna elements may be realized to xe2x80x9csteerxe2x80x9d loci of sensitivity (i.e., transmitting beams or bearings of reception) by establishing predetermined interference patterns among the various patch antenna elements. Prior art coupling structures employed for coupling the respective patch antenna elements with a signal coupling locus (e.g., a transmission line leading to a host device such as a transceiver for radio or radar operations) have heretofore occupied an undesirable lateral expanse about the respective antenna patch elements. As a result, antenna patch elements have not been as densely situated as desired. One solution has been to provide larger antenna patch elements. Installing an antenna patch element that occupies a larger area provides a larger available expanse in the vicinity of that patch element for effecting the requisite electromagnetic coupling and phase shifting of electromagnetic signals. However, the larger the respective patch elements, the less resolution that can be established in steering beam operations. That is, larger patch elements yield coarser beam patterns that result in coarser control of beam steering operations.
Another desired feature for steerable beam antenna device is that electromagnetic signals transferred between the various antenna patch elements and a signal coupling locus (e.g., coupling with a host device) be of equal strength. That is, it is desired that the structure or device that effects the desired distribution does not itself impart a variance to the signals being distributed.
There is a need for a steerable beam antenna device that is small, compact and densely populated with respective antenna patch elements.
An antenna apparatus includes: (a) A radial waveguide parallel with a reference plane and having a first conductive element in parallel spaced relation with a second conductive element. The radial waveguide has a first signal coupling locus for coupling signals with a host unit and a plurality of second signal coupling loci. The radial waveguide distributes signals between the first signal coupling locus and the second signal coupling loci. (b) Signal coupling elements, each presenting a respective signal coupling path for effecting signal coupling association with a respective second signal coupling locus. Each signal coupling path is perpendicular with the reference plane. (c) Antenna elements, each associated with a signal coupling element, each a polygonal element parallel with the reference plane. The radial waveguide element, the signal coupling elements and the antenna elements cooperate to transfer electromagnetic signals between the host unit and a medium adjacent to the antenna elements.
It is, therefore, an object of the present invention to provide a steerable beam antenna device that is small, compact and densely populated with respective antenna patch elements.